Howdy all.

My Ruger AR 10.5" pistol ran fine naked, but when I mounted my suppressor all hell broke loose.  Failures to feed like a big dog.

Friend suggested a different buffer/recoil spring combination.  No idea what's originally in the pistol.  It does have a carbine gas system but no adjustment feature.

He suggested an H1 or "standard" buffer.

Can someone out there confirm what he said or recommend something different?

Thanks

Mike

An adjustable gas block or bolt carrier fixes the over gassed condition without messing with the lower.

The suppressor creates back pressure so it over gassed the gun.  You can tackle that by increasing buffer weight or by tuning the gas via an adjustable gas block, gas key or bolt carrier. I’ve done all the above. The easiest solution is to try a heavier buffer… but I prefer to adjust gas so I can tune the system just right. If you don’t want to mess with the gas block, the Bootleg adjustable carrier works well.

If you have an H2 then try an H buffer. The bolt not going all the way back during cycling can definitely cause a FTF.

No it’s the opposite. The bolt is cycling too fast from the added back pressure from the can. Over gassing symptoms can look like undergassing.

OP:

Describe the malfunction exactly, simply saying a FTF can be interpreted many ways.

Do you have a pic of the spent brass from when the can was mounted?

Here is was I would expect:

Round is fired, and the fired case is about half way extracted out of the chamber and the bolt feeds a round from the magazine into the spent case still in the chamber, smashing it all to hell.

That is the most common type of malfunction I have experienced from being over gassed. You can look at the rim of the spent case and usually it will be bent from the extractor or at least have some nasty claw marks.

The cause of this is because of the excessive back pressure created by the suppressor, the bolt is cycling prematurely when the case is at full obturation (case expanded against the chamber walls). This excessive friction causes the extractor to slip off the rim of the cartridge without fully extracting the case. Then the bolt travels rearward with less energy, but enough to pass the magazine to load a new round into the previously fired stuck brass. Or the bolt travels back just enough for the bottom lug to just barely grab the top round in the mag to get it out of the mag, but then slides forward putting a big ass dent and bending the round as it half assed feeds into the spent case that’s stuck.

Other times, the same basic thing happens as above but the spent case does clear, but again, from the increased friction of extracting during obturation, the bolt doesn’t retract rearward fully and grabs the case at the groove and slides the round out of the mag partially, only to have the bullet hit right below the feed ramp, then bend the round with the bolt stuck and smashed into the round, usually right behind the shoulder.

Again, looking at your spent brass you should see a bent rim or heavy gouges.

Slowing the action down is the solution,

You could even load one round in the mag, then shoot with the can on and see if it locks back. I have had overgassed guns from a can so overgassed the bolt outran the mag catch and didn’t lock back. This exercise would purely be for academic purposes, because at the end of the day, we know you need to slow down the bolt regardless.

This is why the Noveske Switch block, or Bootleg/Gemtech carriers have a “suppressed” setting; to restrict the gas flow thereby slowing the action down.

Adjustable gas block.  Inexpensive, easy to fix and tune when running not suppressed, if that ever happens.  
I had issues when adding cans to my 10.5” inch guns.  Adjustable gas block fixed that.

Mr Chewbacca,

You, sir, have hit the nail square on the head.  What you have described is exactly what I was experiencing.

My thanks to you for describing what I should have done in the first place.  The brass casings were bent to hell and back.

So methinks it's time for me to get my posterior in lockstep with the throng here and get me an adjustable gas block.  

Would y'all have suggestions on WHICH gas block to obtain for my friend the gunsmith to install?  I've heard the Superlative is a good one; I will need something relatively easy to adjust.

My thanks to all that took the time to respond, and I look forward to more replies.

Mike

I like Odin adjustable gas blocks with the click adjustments, not the set screw adjustments, the latter is a pain in the ass. However the Odin doesn’t like to tuck under small ID handgaurds.

Also like SLR Rifleworks. Get the set screw version to make sure it fits under the handgaurd. They use a 2mm adjustment screw, so you can get a long 2mm ball wrench on Amazon to get deep under the handgaurds if needed. This would be my recommendation without knowing the specifics of your set up.

Then there is a specific way to get the gas adjusted correctly. When you get to that step, IM me.

Mr Chewbacca,

Odin adjustable ordered.  I measured the handguard internal dimensions and although tight, this should fit.  Will advise once installed.  

My thanks to all that took the time to respond.

Mike